Gandalf drives off SauronGandalf Drives off Sauron - "Ever most vigilant was Mithrandir, and he it was that most doubted the darkness in Mirkwood, for though many deemed it was wrought by the Ringwraiths, he feared that it was indeed the first shadow of Sauron returning; and he went to Dol Guldur, and the Sorcerer fled from him, and there was a watchful peace for a long while." ~The Silmarillion (Of the Rings of Power and the Third Age)


"'Some here will remember that many years ago I myself dared to pass the doors of the Necromancer in Dol Guldur, and secretly explored his ways, and found thus that our fears were true: he was none other than Sauron, our Enemy of old, at length taking shape and power again.  Some, too, will remember also that Saruman dissuaded us from open deeds against him, and for long we watched him only.  Yet at last, as his shadow grew, Saruman yielded, and the Council put forth its strength and drove the evil out of Mirkwood-" ~The Fellowship of the Ring, Book II, chap. 2 (The Council of Elrond)